The present invention relates to a non-contact reading type IC card with a pre-enhancement function and, more particularly, to an IC card in which the signal transfer characteristic between the IC card and an external reading unit is improved.
A card-like medium (IC card) has recently been developed which incorporates an IC (integrated circuit) having a large storage capacity. Efforts have been made to put such a medium into practical use in various data managements for transactions and the like. In order to perform a signal transfer between the IC card and the external reading unit, a non-contact type IC card of a magnetic coupling system has been developed in place of a conventional contact type IC card of an electrical contact system.
The contact type IC card poses a problem of reliability whereas the non-contact type IC card of the magnetic coupling system has improved reliability. In addition, according to the non-contact type IC card, a reading unit for the conventional IC card which is widely used at present can be utilized without any modification.
According to this magnetic coupling system, a thin film magnetic head, i.e., a transducer including a coil for generating a magnetic field is formed on an insulating card-like substrate incorporating an IC, and a pulse signal (information) is supplied from an output port in the IC card to the coil of the transducer. As a result, a magnetic field corresponding to the signal is generated in the coil or in a magnetic gap of the transducer. On the other hand, in a reading unit for reading internal information output from the IC card, a magnetic head of the reading unit is positioned near the coil or a core gap portion of the transducer of the IC card to detect changes in the magnetic field generated at the transducer of the IC card. With this arrangement, changes in current induced by the coil of the magnetic head of the reading unit correspond to signals output from the IC card.
However, according to the signal transfer system of the IC card system described above, the following problem is posed. When a pulse signal having a rectangular waveform shown in FIG. 3A is output from the IC card side, the magnetic head of the reading unit may output a pulse having ringing components at its leading and trailing edges, as shown in FIG. 3B. For this reason, data processing performed by shaping such a waveform is hindered. The reason for this may be as follows. In the reading unit used together with the conventional magnetic card, a frequency characteristic of an amplifier for amplifying a signal output from the IC card after the output signal is detected by a magnetic head is not flat in a high-frequency range. Since the reading unit including such an amplifier having a non-flat high-frequency range characteristic is presently used for reading output data from the IC card, some countermeasures must be taken on the IC card side.